The present study deals with the acquisition of the epistemic reading of the modal verb "können" in child language. The class of modal verbs, to which "können" undoubtedly belongs, has always eluded simple description. German modal verbs exhibit a particular inflection. Semantically, they are consistently polyfunctional, as they have both circumstantial and epistemic (or evidential) meanings. Furthermore, their semantics is difficult to distinguish from that of their system competitors (modal adjectives, modal adverbs). Lastly, the syntactic relationship between the modal verb and the governed infinitive can vary significantly. In addition, the acquisition of epistemic readings poses a very high cognitive demand on the child in terms of forming a (subjective) theory of probability.